This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-350021, filed Dec. 9, 1999, the entire contents of which are incorporated herein by reference.
The present invention relates to a method of manufacturing a semiconductor device having a plurality of columnar electrodes and a sealing film filled between these columnar electrodes, on its surface.
A semiconductor device such as of a type called CSP (Chip Size Package) is typically manufactured as shown FIGS. 3A to 3C. A semiconductor substrate 1 in the form of wafer, which is made of silicon or the like, having a plurality of columnar electrodes 2 made of copper or the like, made on its upper surface thereof, is prepared, and a sealing film 3 made of an epoxy-based resin is formed thereon such as to cover the surrounding area of the columnar electrodes 2 on the upper surface of the substrate by a molding method or spin-coat method, or the like, as shown in FIG. 3A. Subsequently, the upper surface of the sealing film 3 is polished so as to expose the upper surface of each of the columnar electrodes 2 as shown in FIG. 3B. Then, a surface treatment layer 4, which serves as an oxidization preventer, is formed on the upper surface of each columnar electrode 2 by non-electrolytic plating as shown in FIG. 3C. Lastly, the semiconductor substrate 1 is diced, and thus individual semiconductor devices are obtained.
FIG. 4 shows a cross section of an example of a state in which a semiconductor device 5 obtained in the above-described manner, is mounted on a circuit substrate 6. In this example, the surface treatment layer 4 provided on the lower surface of each columnar electrode 2 of the semiconductor device 5 is connected to a connection terminal 7 set at a predetermined location on the upper surface of the circuit substrate 6 via solder (paste) 8 provided in advance on the connection terminal 7 by a screen printing method.
In the conventional semiconductor device manufacturing method described above, the columnar electrodes 2 undesirably differ in size from one to another, and therefore in environmental tests such as temperature cycle and the like, the bonding strength cannot be made uniform among the columnar electrodes 2 connected via bonding to the respective connection terminals 7. Consequently, the conventional method is not very much reliable. According to the analysis of the factor for such an unreliability, it has been confirmed that it is due to the occurrence of an uneven protrusion or laterally broadened edge 2a on the upper side of each of the columnar electrodes 2 as indicated in, for example, FIGS. 5A and 5B when the upper surface of the sealing film 3 is polished to expose the upper surfaces of the columnar electrodes 2. When such a protrusion 2a is created on the upper side of each columnar electrode 2 and thus the shape of the upper surface of each electrode is deformed, the flat shape of the surface treatment layer 4 formed thereon is also affected and deformed. As a result, the shape and area of the vicinity of the bonding section to the connection terminal 7 of the circuit substrate 6 vary from one case to another, which creates a difference in the bonding strength. Therefore, the reliability against changes in environment of the devices manufactured by the method is lowered.
The object of the present invention is to form the upper surfaces of columnar electrodes as initially designed, thereby achieving a uniform bonding strength among the electrodes and improving the reliability of the product.
According to the present invention, there is provided a method of manufacturing a semiconductor device, comprising the steps of:
preparing a semiconductor substrate on one surface of which a plurality of columnar electrodes are formed;
forming a sealing film on the one surface of the semiconductor substrate for covering sections between the columnar electrodes and the columnar electrodes themselves; and
polishing an upper surface of the sealing film until upper surfaces of the columnar electrodes are exposed; and
removing laterally broadened edges formed on the upper sides of the columnar electrodes which have been formed by the polishing by etching the upper surfaces of the columnar electrodes.
According to the present invention, the laterally broadened edges or protrusions formed on the upper sides of the columnar electrodes are removed by etching, and therefore the shape of the upper surface of each columnar electrode can be formed as initially designed, thereby making it possible to achieve unifying the bonding strengths in the electrodes and improve the reliability.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.